The present invention relates generally to electronic printers and, more particularly, a driving mechanism for use in such printers which mechanism effectively and efficiently reversibly reciprocates, at different speeds, a carriage holding image recording material.
This invention relates to an improvement of an electronic printer of the type described in commonly assigned and copending application U.S. application Ser. No. 158,585 entitled "ELECTRONIC IMAGE PRINTING APPARATUS", filed Feb. 22,1988 by Lawrence M. Douglas. As described in said application, the electronic printer includes a film carriage which reciprocates at a constant speed, by a common drive mechanism, between a start printing position and a film processing position. Removably mounted on the film carriage is a film pack or cassette containing a plurality of stacked individual film units of the self-developing kind, such as manufactured by Polaroid Corporation. The film carriage advances linearly at a very slow rate to define a slow scan movement. During the slow scan movement, beams of light are scanned quickly across the image areas of each film unit in registry with the film pack aperture. This fast scanning is in a direction generally transverse to the slow scan direction. The combination of the fast and slow scan movements provides for raster scan imaging on individual ones of the film units. The film carriage is driven at a constant speed by a common motor and lead screw arrangement.
While the above driving mechanism functions satisfactorily, it is desired, in certain situations, to increase the return speed of the film carriage to the start printing position following movement thereof to the film processing position. Such an increase would, of course, increase the total number of film units which could be printed per unit time.
It is, therefore, desired to provide a driving mechanism which not only reversibly reciprocates the film carriage at different speeds, but can achieve the foregoing in a manner which is simple and compact in construction and which does not add significantly to the overall cost of the printer. Another important factor is that such a drive mechanism must be reliable enough to hold precision of the slow scan movement so as to avoid undesired pixel placement deviation.